Device for the correction of river beds



Feb. 2, 1965 J. CHABERT ETAL DEVICE FOR TRE CORRECTION OF RIVER BROS Filed April 25, 1961 m N m Am cun J tv w A. 11%. M .JA mwu..

United States Patent C 3,167,922 DEVICE FR THE CORRECTIN OF RIVER BEDS Jacques Chabert and Maurice Remllienx, Paris, France, assignors to Electricite de France (Service National), Paris, France, a French national service Filed Apr. 25, 1961, Ser. No. 105,467 Claims priority, application France, May 3, 1960, 826,022 3 Claims. (Cl. 61-2) The invention relates to a device for the correction of river beds, which in particular makes it possible to form a channel across an alluvial shelf which separates an upstream deep from a downstream deep and obstructs navigation when the waters are at their normal level or low.

It is known, notably from the works of Potapov and Pychkine published in the U.S.S.R., that it is possible to form channels in obstacles made up of accumulated sand and gravel, by placing structures on the river bed near to these obstacles. These structures articially form secondary currents which increase the opportunities for the flow in the vicinity of these obstacles to carry off silt. These structures on the river bed are in the form of long, submerged breakwaters or else of short structures arranged on either side of a line followed by the flowing of the waters.

The present invention aims to create a device which will make it possible to form channels in river beds, also by forming secondary currents, but which are set up and made so as to give greater efficiency than the known devices of this type.

The striking feature of a device according to the invention is that it comprises a series of spaced screens planted in the river bed, the upstream ends of these screens all being placed along a continuous curve which crosses the alluvial shelf following a line taken by the currents for the period of normal water level, these screens all being arranged at the same side of this curve and being positioned so that they each form an acute angle with the tangent to the said curve at their upstream end.

In a period of normal water level, such a device gives rise to the formation of a secondary, helical current crossing the entire alluvial shelf; this helical current rises opposite the first upstream screen and is taken up and continued by all the other screens situated downstream to it. By the erosive action of this secondary current a channel is formed, when the waters are subsiding, along the entire length of the curve on which the upstream ends of the screens are planted, the channel being on the side of the curve opposite to the screens.

The features and advantages of the invention will be brought out in the following description which serves as an example and refers to the enclosed drawing, in which:

FIG. l is a diagrammatic plan of a part of a river provided with a device according to the invention;

FIG. 2 shows the positioning of the screens which constitute this device;

FIG. 3 is a diagrammatic vertical section of the device;

FIG. 4 is a vertical section of an embodiment of a screen.

According to FIG. 1, a device according to the invention is installed in a river which has, between an upstream deep 12 and a downstream deep 14, an alluvial shelf 16 likely to hinder navigation at normal or low water.

As is known, the direction in which the water flows above the shelf, which when the river is swollen is substantially parallel to the banks 1S (arrow 20), becomes progressively oblique as the waters subside (eg. line 22).

The device according to the invention comprises a series of spaced deviating screens 24 planted in the bed of thev river. According to FIG. 2, the upstream ends 26 of 3,167,922 Patented Feb. 2, 1965 ICC these screens are all placed along a continuous curve 28 which crosses the alluvial shelf following a line in which the surface currents travel when the waters are at their normal level; these screens are all arranged at the concave side of the curve 28 and are positioned so that they each form an acute angle with the tangent 30 to the curve at their end 25.

The screens 24 give rise, at the bottom of the river, to a secondary helical current crossing the whole shelf 16. The screen 24 situated the farthest upstream starts creating the helical movement, which is then taken up and continued by the other screens. By the silt-carrying action of this secondary current a channel 32 (FIG. 1) is formed along the entire length of the curve 28 on which the heads 26 of the screens are planted, on the side of this curve opposed to the screens.

Experience has shown, notably in the course of experiments conducted on the sandy shelves of the Niger between Koulikoro and Segou (Sudanese Republic), that the best results are obtained by choosing a curve 28 which corresponds to an average line of current for the maximum speeds at normal water level, and by positioning the screens so that their angle of attack with the current is variable between 30 and 5 during the period of normal water level; the dotted arrows in FIG. 2 show the directions of the current corresponding to the absolute limits of the screens effectiveness; the mean curve 28 is included between these arrows.

During the tests conducted, the screens 24 consisted of rectangular panels made of thin sails (FIG. 3 and 4) arranged vertically and hooked at 40 onto stakes 41 planted in the bed 34 of the river. It was noted that it was advantageous to give them a length I of between l0 and 50 metres (e.g.v 25 metres), to space their ends upstream at a distance L equal to about two and a half times this length, and to give them a height lz of between 30 and 50% of the draught of water H present during the period of normal water level when the formation of the channel is required to commence; during the tests this height was between 1 and 2 metres, and preferably equal to 1.50 metres for a draught of water equal to 4 metres at a period of normal water level.

During the tests it was possible, while the water was subsiding, to effect excavations of 0.50 to 1 metre in shelves several hundred metres in length, which made it possible to form a navigable channel 32. Navigability was thus prolonged when the waters were low, since the shelves benefit from an extra draught of water of at least 0.50 m., whereas in the natural state the draught of water can decline to 0.20 m.

The invention is of course not restricted to the embodiment chosen and illustrated, which was given purely by way of example but which can on the other hand, within the framework of the invention, be made the object of several variations.

Among other variants one can in particular envisage, for instance, screens of different shapes: for instance curved in plane View, inclined to the vertical, variable in height, provided with an overhang at their upper edge. It will also be noted that the device according to the invention can be used to protect water intakes from silting up. By judicious positioning it is also possible, on the other hand, to create localised silting-up; this effect is used, for instance, to protect a bank from erosion. The same effect is used in the case of FIG. 1 (panels 38) to maintain the position of the upstream deep and thus to extend the useful life of the device 24.

We claim:

l. A device installed in a river for forming a channel therein, said river having an upstream deep and a downstream deep and an alluvial shelf which separates the upstream deep from the downstream deep and is less deep than said deeps, the river having a rst horizontal direction of iioW generally parallel to the river banks at high water and a second horizontal direction of flow having a lower water level than said ow of said first direction and moving from said upstream deep to said downstream deep and across said alluvial shelf at an angle to said rst direction, said device comprising a series of spaced screens having horizontally elongated substantially vertical side faces upstanding from said alluvial shelf, the series of screens extending across the shelf from the upstream deep to the downstream deep with their directions of elongation extending in the general direction of said second direction, each screen having an end upstream relative to the other end thereof and being on the end toward the upstream deep, the upstream side faces of said screens with regard to said first direction of flow crossing a portion of the path of flow of Water moving in said iirst direction, the upstream ends of said screens with regard to said second direction of flow lying on a line parallel to said second direction, the downstream ends of said screens with regard to said second direction of ow being displaced from said line in a direction that is upstream with regard to said rst direction of ow and by a distance such that said upstream side faces form acute angles with the portion of said line which is downstream of the respective screen thereby to induce helical currents that move in said second direction to form in said shelf` a channel that is disposed parallel to said line and that interconnects said upstream and said downstream deeps and is disposed downstream of said screens with regard to said iirst direction of ow.

2. A device as claimed in claim 1, in which said acute angles are about 5430".

3. A device as claimed in claim 1, in which said upstream ends of the screens are spaced apart a distance equal to about two and one-half times the length of the screens. v

References Cited in the iile of this patent UNITED STATES PATENTS 104,586 Harlan June 21, 1870 195,896 Knapp Oct. 9, 1877 320,129 Goodridge June 16,1885 875,487 Audouin Dec. 31, 1907 -1,812,300 Leeds et al. June 30, 1931 1,858,231 Parshall May 10, 1932 2,032,582 Lashmet Mar, 3,1936 2,931,183 Riviere Apr. 5, 1960 FOREIGN PATENTS 4,199 f' Great Britain of 1884 23,118 Great Britain 1893 193 Great Britain Jan.v 4, 1909 110,507 Great Britain Oct. 25, 1917 

1. A DEVICE INSTALLED IN A RIVER FOR FORMING A CHANNEL THEREIN, SAID RIVER HAVING AN UPSTREAM DEEP AND A DOWNSTREAM DEEP AND AN ALLUVIAL SHELF WHICH SEPARATES THE UPSTREAM DEEP FROM THE DOWNSTREAM DEEP AND IS LESS DEEP THAN SAID DEEPS, THE RIVER HAVING A FIRST HORIZONTAL DIRECTION OF FLOW GENERALLY PARALLEL TO THE RIVER BANKS AT HIGH WATER AND A SECOND HORIZONTAL DIRECTION OF FLOW HAVING A LOWER WATER LEVER THAN SAID FLOW OF SAID FIRST DIRECTION AND MOVING FROM SAID UPSTREAM DEEP TO SAID DOWNSTREAM DEEP AND ACROSS SAID ALLUVIAL SHELF AT AN ANGLE TO SAID FIRST DIRECTION, SAID DEVICE COMPRISING A SERIES OF SPACED SCREENS HAVING HORIZONTALLY ELONGATED SUBSTANTIALLY VERTICAL SIDE FACES UPSTANDING FROM SAID ALLUVIAL SHELF, THE SERIES OF SCREENS EXENDING ACROSS THE SHELF FROM THE UPSTREAM DEEP TO THE DOWNSTREAM DEEP WITH THEIR DIRECTIONS OF ELONGATION EXTENDING IN THE GENERAL DIRECTION OF SAID SECOND DIRECTION, EACH SCREEN HAVING AN END UPSTREAM RELATIVE TO THE OTHER END THEROF AND BEING ON THE END TOWARD THE UPSTREAM DEEP, THE UPSTREAM SIDE FACES OF SAID SCREENS WITH REGARD TO SAID FIRST DIRECTION OF FLOW CROSSING A PORTION OF THE PATH OF FLOW OF WATER MOVING IN SAID FIRST DIRECTION, THE UPSTREAM ENDS OF SAID SCREENS WITH REGARD TO SAID SECOND DIRECTION OF FLOW LYING ON A LINE PARALLEL TO SAID SECOND DIRECTION, THE DOWNSTREAM ENDS OF SAID SCREENS WITH REGARD TO SAID SECOND DIRECTION OF FLOW BEING DISPLACED FROM SAID LINE IN A DIRECTION THAT IS UPSTREAMS WITH REGARD TO SAID FIRST DIRECTION OF FLOW AND BY A DISTANCE SUCH THAT SAID UPSTREAM SIDE FACES FORM ACUTE ANGLES WITH THE PORTION OF SAID LINE WHICH IS DOWNSTREAM OF THE RESPECTIVE SCREEN THEREBY TO INDUCE HELICAL CURRENTS THAT MOVE IN SAID SECOND DIRECTION TO FORM IN SAID SHELF A CHANNEL THAT IS DISPOSED PARALLEL TO SAID LINE AND THAT INTERCONNECTS SAID UPSTREAM AND SAID DOWNSTREAM DEEPS AND IS DISPOSED DOWNSTREAM OF SAID SCREENS WITH REGARD TO SAID FIRST DIRECTION OF FLOW. 